Packaging



R. L. DREYFUS Oct @8, 1968 PACKAGING '2 Sheets-Sheet 1 Original FiledJuly 24, 1961 FIGS? 1968 R. L. DREYFUS 3,404,503

PACKAGING v Original Filed July 24, 1961 2 Sheets-Sheet 2 H4- 1 1 l II02: '09 a ,H.

FIGJI United States Patent 3,404,508 PACKAGING Robert L. Dreyfus,Arlington, Mass., assignor to W. R. Grace & Co., Cambridge, Mass., acorporation of 1 Connecticut Application July 24, 1961, Ser. No.126,202, now Patent No. 3,215,266, dated Nov. 2, 1965, which is acontinuation-in-part of application Ser. No. 772,471, Nov. 7, 1958.Divided and this application Sept. 15, 1965, Ser. No. 527,999

2 Claims. (Cl. 53-34) ABSTRACT OF THE DISCLOSURE A method of covering anobject by placing the object on a heat-shrinkable film, bringing theedges of the film over the top of said object, and heating the edges toshrink them and form a thickened edge on the film.

This invention relates to packaging and more particularly, to thepackaging of one or more articles within a sheet of heat-shrinkable,thermoplastic material.

This application is a division of my prior copending application Ser.No. 126,202, filed July 24, 1961, now U.S. Patent 3,215,266 dated Nov.2, 1965, which was a continuation-in-part of my application Ser. No.772,471, filed Nov. 7, 1958, now US. Patent 3,060,655 dated Oct. 30,1962.

It is an object of the present invention to provide a novel and simplemethod of enclosing an object within a sheet of heat-shrinkable,thermoplastic material.

An additional object is to partially encapsulate objects usingheat-shrinkable plastic material.

A further object is to package together a plurality of objects using aheat-shrinkable, thermoplastic film sheet.

It is also an object to package together a plurality of objects withoutthe use of supports or trays of any kind.

It is also an object of the present invention to package together aplurality of objects utilizing the heat-shrinking properties of thethermoplastic wrapping material to hold the wrapping material in placeabout the objects.

Still further objects and the entire scope of applicability of thepresent invention will become apparent from the detailed descriptiongiven hereinafter. It should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

Referring to the drawings:

FIGURE 1 is a plan view showing a preliminary step in the packaging of aplurality of objects which are somewhat spherical in shape;

FIGURE 2 is a sectional view showing a later step in the formation ofthe same package;

FIGURE 3 is a perspective view showing the completed package;

FIGURE 4 is an elevational view, partially in section, of a modifiedform of the package shown in FIGURE 3;

FIGURE 5 is a perspective view of a package enclosing a plurality ofcylindrical objects;

FIGURE 6 is an elevational view, partially in section, of a packageenclosing a cylindrical object;

FIGURE 7 is a sectional view of an alternative method of forming a coveraround a container;

FIGURE 8 is a sectional view of the cover at the completion of theprocess in FIGURE 7;

FIGURE 9 is a vertical section showing the partial encapsulation of aring gasket;

"ice FIGURE 10 is a perspective view showing the forma tion of anoverwrap;

FIGURE 11 is a side elevational view showing the sealing of the overwrapof FIGURE 10;

FIGURE 12 is a elevational view of a cylindrical container spirallywrapped with heat shrinking film; and

FIGURE 13 is a perspective view of an object packaged according to thepresent invention.

In the present invention, a single object or a plurality of objects arepackaged using a heat-shrinkable, thermoplastic film as the solepackaging material. Suitable heatshrinkable polymeric film materials, asare well-known t those skilled in the art, include, but are not limitedto, such materials as heat-shrinkable polyolefins, e.g., polypropylene,polyvinyl compounds, e.g., polyvinyl chloride and sarans, polyesters,e.g., polyethylene terephthalate.

The heat-shrinkable plastic material is employed in the form ofrelatively thin sheets, i.e., from 0.5 mil to 3 mils in thickness, whichsheets may be transparent, translucent, colored, printed, etc., asdesired.

Heat-shrinking properties are produced in some thermoplastic polymericmaterials by heating the solid polymer to an elevated temperature,stretching the heated polymer thereby stretching and orienting themolecules in the polymer, cooling the polymer While under thisstretching tension to a temperature at which the polymer will retain itsstretched or oriented state when tension is released. In effect, themolecules in the polymer are aligned and stretched in the direction ordirections in which they are drawn and frozen in. this new position. Thesubsequent application of heat to the polymeric material thaws thepolymer and permits the polymer molecules to return to their originalpre-oriented position or state.

In the specific examples below, there is employed as the heat-shrinkablefilm, irradiated, biaxially oriented polyethylene, prepared from Alathon14 which is a polyethylene having an average molecular weight of 20,000and a density of 0.916. The polyethylene is irradiated to an extent ofabout 12 megarad and then biaxially stretched 350 percent longitudinallyand 350 percent laterally. The thus irradiated and stretchedpolyethylene has a shrink energy of about pounds per square inch in bothdirections at 96 C. and has a tensile strength of at least 5,000 poundsper square inch at 21 C. The high tensile strength and high shrinkenergy make this film particularly suitable for use in the presentinvention.

Referring more specifically to FIGURES l, 2, and 3 of the drawings,there is provided a fixture 21 which serves merely as an aid in theformation of the package of the present invention. The fixture is arectangular frame open at top and bottom which is sufficiently large toencompass the objects being packaged.

A sheet 22 of the irradiated, oriented polyethylene film, 1.0 mil thick,is placed over the fixture as shown in FIGURE 1. Six, roughly sphericalobjects 23, e.g., oranges, are placed in the fixture over that portionof the film sheet within the fixture. One end 24 of the film sheet isfolded up against the side and over the top of the objects. The oppositeend 25 is subsequently drawn over the top of the objects, overlappingthe first fold and is then drawn down against the side of the objects.The film end 25 is held between the fixture and the objects 23 as isshown in FIGURE 2. The objects are now enclosed within a sheet ofshrinkable film, two longitudinal ends of which are overlapped so as toform a somewhat loose tube which is open at both ends. The overlappededges preferably extend over the convex surfaces of the en closedobjects as shown in FIGURES 2 and 3. The fixture, containing the objectsenclosed within the tube of film, is passed through a hot air oven, thetemperature of which is high enough to shrink the particular filmemployed. In the present example, an air temperature of 500 F. wasemployed. Surprisingly, the overlapped longitudinal film edge inshrinking does not slide over the underlying film causing the tube tocome apart but rather the overlapped film edge shrinks against andbecomes locked to the underlying film at points where the edges overlapand bear against the enclosed objects. The heat required to shrink thefilm combined with the tension exerted by the shrinking film issufiicient to provide a positive heat seal. The open ends of the tubeshrink back against the object, gripping the objects but leaving a smalloval opening, the film edges of which are somewhat thickened. Thecompleted package with the fixture removed is shown in FIGURE 3.

The above package is particularly suitable for horticultural itemsbecause of the opening at either end which permits circulation of airthrough the package. It is also possible to package non-horticulturalitems in the above package.

The above package is formed without the fiber or pulp tray commonly usedin packaging fruits, vegetables, etc. This in itself is a tremendousadvantage in that it eliminates the cost of the tray, results in apackage that is formed from a single material, requires no adhesives,clips or any other additional fastening means and provides a packagewherein the product is completely visible from all sides. Anotherunexpected advantage is that the above package withstands the abuses ofhandling and shipping to a much greater extent than does theconventional, pulp tray-film overwrap, type of package. In addition, inmy package there is no problem of fitting the objects to the packagewhich problem does exist when trays are a necessary part of the package.

It is possible to obtain a strong, fairly rigid package without thenecessity of a tray or some other reinforcing means because the filmshrinks about the enclosed objects tightly and does not relax thistightness and thereby holds the objects together in a fixed or stableposition.

It is not necessary that the objects all lie in a single plane as inFIGURE 3 but the objects may be stacked in layers. In FIGURE 4, forexample, two of the objects are stacked upon a base of four objects. Anoversized sheet of 1.5 mil irradiated, biaxially oriented polyethylenefilm 41 is drawn around the stacked spherical objects 42 so that onelongitudinal edge overlaps the opposite longitudinal edge. It isdesirable that the film edge overlap the underlying film by at leastthree inches and preferably by a distance at least equal to the diameteror thickness of the objects being enclosed. Preferably the overlappedfilm portions should overlay the convex portions of the sphericalobjects. The overlapped film edge may be held in place for passagethrough a hot air oven by causing the overlapped portion to bepositioned beneath the objects. The weight of the objects will preventthe tube from opening. The film shrinks, as in the previous example,forming a tight, stable package in which the overlapped longitudinaledge 43 is heat sealed where tension has been brought to bear by theshrinking film. The heat seal does not extend along the entirelongitudinal edge but occurs only where the overlap occurs across aconvex surface so that the shrinking of the film presses the layers ofthe film tightly together.

As already indicated, the overlapped longitudinal edges of the filmsheet should preferably overlay a convex or protruding portion orsurface of the object or objects, so that when shrinking occurs, amechanical cup-like locking of the overlapped film edges takes place. Asthe film shrinks, the overlapped film portions are forced into intimatecontact over all convex or protruding surfaces, and a seal occurs inthese areas due to the combined effects of heat and pressure.

It may be desirable to first shrink the open ends of the tube as thiswill function to lock the film tube about the enclosed objects andprevents the overlapped portions '4 from blowing out of contact whenexposed to the hot air. It has been found that in many cases when theproduct, enclosed within the tube, is run through a hot air oven ortunnel that the ends will tend to shrink first because there is nonearby material to absorb heat transmitted to the film. Therefore, whatappears to be a simultaneous overall application of heat will stillafford the desired result.

The objects that may be packaged in this manner include single objects,multiple objects, and multiple packages containing such objects. Theobjects are not limited to those having any particular shape, size orcomposition.

A plurality of cylindrical containers may be advantageously packagedtogether in the manner of the present invention as is shown in FIGURE 5of the drawings. Three cylindrical containers 51 are placed together ina straight row upon an oversized sheet of heat shrinkable film 52. Thefilm is wrapped longitudinally about the containers by first bringingone longitudinal film edge 53 across the top and partially down the sideof the containers and then bringing the opposite longitudinal film edge54 over the top of the containers overlapping the first film edge andextending a short distance down the opposite side of the containers. Theoverlapped film edge 54 extends at least one-half inch down the side ofthe container. It is preferable that the overlapped film edgescompletely cover the tops of the containers. The open ends of the filmwrapper extend at least two inches beyond either end of the row ofcontainers. The open ends 55 of the film are first shrunk by directinghot air from a hot air gun at these ends, shrinking them back againstthe containers. By shrinking the ends first, this will serve to hold theoverlapped film edge in place. The entire package is then subjected tohot air shrinking the heretofore unshrunk portions of the wrapping sheetand causing the overlapped edge to be heat-sealed to the underlying filmsheet in those areas where the overlapped film layers bear against theenclosed containers and particularly in those areas where the overlappedfilm edges bear against a convex surface. The only purpose inpre-shrinking. the ends is to prevent the overlapped edge from openingup prior to the main shrinking operation or to prevent the overlap fromblowing away from contact with its mating or underlying film surface orshrinking out of contact with the underlying surface when exposed to ahot air blast. A slight mechanical pressure will also sufiice to keepthe overlap in place and in contact with the underlying surface.Sufficient pressure may be provided by resting the package on theoverlapped portion during shrink; another method would be to place alight weight on top of the containers, e.g., a conveyor belt which rideson top of the overwrapped containers as they pass through a hot airtunnel.

Partial encapsulation of a single cylindrical object, e.g., a roll ofpaper can be accomplished by placing the roll 61 upon an oversized sheetof shrinkable film 62, overlapping the longitudinal ends of the film andshrinking the protruding ends of the tube back against the roll. Theremainder of the film is heat shunk producing a tight, wrinkle-freepackage in which the overlapped film edge 63 is held tightly against theunderlying film surface, as shown in FIGURE 6.

Using a long, narrow strip of irradiated, high shrink energypolyethylene, it is possible to encapsulate objects as is shown inFIGURE 12. A sheet 81 of the polyethylene having a thickness of 1 mil isspirally wrapped around cylindrical container 82. Opposite ends 83 and84 of the sheet are heated, e.g., with the aid of a radiant heater 85,and thus shrunk to secure the package. Then the remaining surfaces ofthe polyethylene sheet are heat-shrunk around the cylinder to completethe encapsulation procedure. The application of heat will partially sealthe overlap.

The present invention is also adapted to placing a protectivepolyethylene film on lids or covers. This form of the invention isillustrated in FIGURES 7 and 8. Thus, a form or ring 71 for making a lidor cover is placed top side down on a piece of irradiated, high shrinkenergy, polyethylene film 72. The edges of the lid 71 and thecorresponding area of the polyethylene film are restrained by means ofring 73. The free polyethylene film 74 on the back 75 of the lid isheated with hot air heater 76 to shrink and thicken the polyethylene at77, as shown in FIGURE 8. The restraining ring acts to control theshrinkage, since shrinkage does not take place under it or beyond. Inorder to remove wrinkles from the polyethylene film, the front of thelid can be heated briefly as can the sides and the area under the ring.In similar fashion, the polyethylene film 91 can be shrunk around gasket92 to form a thickened sealing area 93 at the back, as shown in FIGURE9.

The present invention can likewise be used to cover only one surface andthe sides of a package, the back surface being sealed only at the fourcorners as is illustrated in FIGURES l and 11. As an illustration ofthis procedure, a box inches by 8 inches by 1% inches was packaged usingan irradiated, high shrink energy, polyethylene film 9 /z inches wide by12 /2 inches long. These dimensions were obtained by utilizing as thewidth, the box width plus two times the box height plus two inches, andas the length, the box length plus two times the box height plus twoinches. The box 101, top side 102 down, was centered on the polyethylenefilm 103 with the long side 104 of the box parallel to the long side ofthe film. One opposite pair of film edges, e.g., the two long edges 105and 106, were folded over the box. Then the second pair of film edges,namely the short edges 7 and 108, were folded over the box. At the fourcorners, these edges overlapped. The box 101 was then inverted on aTeflon (po'lytetrafiuoroethylene) 109 covered hot plate 111. The hotplate was set at about 300 to 325 F. and weight 112, biased by spring114, was pressed down firmly on the overlapping edges to heat the filmuniformly. The film is sealed at the four corners and shrunk along theborders with a resultant increase in gauge and tightness. The filmshould be cooled while the film is still being restrained. Normaloverwrapping, e.g., the diaper wrap, requires 14 inches by 14 inches(196 square inches) or more of polyethylene film. The present procedurethus results in a saving of 40 percent or better in material required.

A modification of the above methods produces the package illustrated inFIGURE 13, wherein an object 111, e.g., a head of lettuce, is completelywrapped in a sheet of heat-shrinkable, irradiated polyethylene 112. Thehead of lettuce placed upon an oversized sheet of film and wrapped bythe diaper wrap method, i.e., opposite diagonal corners of the filmsheet are folded over the object. The folds 113 were made withouttucking so that the package was quite loose. The package was placed on aflexible wire conveyor belt with the folds in contact with the belt sothat the weight of the product would hold the fold from shrinking apartduring the shrinking and sealing process. The product loosely wrapped iscarried through a high-temperature, 800 F., 1000 feet per minute, hotair shrinking tunnel at a speed of 60 feet per minute. The folds 113seal together during the shrinking operation, and the remainder of thefilm closely clings to the head of lettuce. This procedure eliminatesthe separate sealing operation for the overlapped film corners or anyother sealing or securing step such as fastening with clips, glue, etc.

In general, there is employed as the wrapping material in this inventiona polyethylene film which has been irradiated to an extent of 2 to 100megarads, preferably 6 to 20 megarads. This irradiation can beaccomplished in conventional fashion, e.g., by the use of an electronbeam generator, such as the 2,000,000 volt. General Electric resonanttransformer unit or other high energy particle generators of from 50,000to 50,000,000 volts or a Van de Graaff electron generator. In additionto the use of electrons, there may be employed beta rays, gamma rays,etc. There can be employed any of the irradiation procedures disclosedin Baird application, Ser. No. 713,848, filed Feb. 7, 1958, or in Raineret al., United States Patent 2,877,500. The disclosures to the Rainer etal. patent and the Baird et al. application are hereby incorporated byreference.

The biaxial orientation is normally carried out to an extent of 100percent to 700 percent longitudinally and 100 percent to 900 percentlaterally. The biaxial stretching can be carried out by blowingirradiated polyethylene tubing as disclosed in the Baird application.The irradiated biaxially oriented polyethylene prepared by such aprocedure has a high shrink energy, e.g., 100 to 500 pounds per squareinch in each direction at 96 C. Shrink energy is defined as the force ofcontraction at a given temperature when the material is restrained, morespecifically, it is the measurable tension produced in a fullymonodirectionally restrained strip of film when heated to the specifiedtemperature.

There can be employed as the starting polyethylene for the irradiationprocedure high, low or medium density polyethylene prepared by high orlow pressure techniques and having molecular Weights of from 7000 tomore than 35,000.

There may also 'be employed in place of polyethylene in the irradiationprocedure, copolymers of ethylene and propylene, copolymers of ethylenewith minor amounts of other vmon-olefins or butadiene and also blends ofpolyethylene with copolymers of ethylene and other monoolefins, e.g.,polyethylene blended with from 25 percent to percent by weight of acopolymer of ethylene copolymerized with from 0.5 percent to 15 percentby Weight of an olefin having 3 to 18 carbon atoms.

Other heat-shrinkable film materials which may be employed includeoriented polypropylene, polyvinyl chloride, and vinylidene chloridecopolymers, etc.

I claim:

1. A method of covering an object comprising:

(a) placing the object on a heat-shrinkable film;

(b) bringing the edges of the film over the top of said object;

(c) restraining the film at the top edges of the object;

(d) heating the free portion of the film to shrink it back to saidrestrained portion and form a thickened edge on the film; and,

(e) ceasing said restraining of the fil-m at the top edges.

2. A method according to claim 1 wherein said object is a circularcontainer.

References Cited UNITED STATES PATENTS 7/1956 McCarty 20645.33 5/1962Carpenter et al. 53-184

